<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <div id="app">
    <button v-on:click="count--">-</button>
    <span>{{ count }}</span>
    <button @click="count++">+</button>
  </div>
  <script src="https://cdn.jsdelivr.net/npm/vue@2.7.14/dist/vue.js"></script>
  <script>
    // 目标: 点击 - 让数字减一, 点击 + 让数字加一
    const app = new Vue({
      el: '#app',
      data: {
        count: 100
      }
    })
  </script>
</body>

</html>